var arr =[1,'dfg',3.345,'东方国际']
console.log(arr.length);
arr.length=100;
  
for (var i = 0; i < arr.length-1; i++) {
    console.log(arr[i]);
}

arr.unshift('&&&&&','狗屁🐷不是')
console.log(arr);
for(var i=0;i<100;i++)
{
    arr.shift()
}
console.log(arr);

var cc='ERTout'
console.log(cc.toUpperCase());

console.log(cc.indexOf('T'));

console.log( cc.substring(2,3));
console.log( cc.substring(3));

var num=['A','C','B','D']
console.log(num);
